At least 10 dead in shooting at Santa Fe High School in Texas, 17-year-old suspect in custody

The suspect has been identified as 17-year-old Dimitrios Pagourtzis, law enforcement sources told CBS

A Texas teen dressed in a trench coat carried out another horrific school shooting Friday, killing 10 people and wounding 10 more while armed with a handgun, a shotgun and a chilling stash of explosives, authorities said

Dimitrios Pagourtzis, 17, gunned down nine students and a teacher in the massacre at Santa Fe High School about 30 miles south of Houston just as classes were starting for the day, officials said.

Pagourtzis used firearms owned by his father and initially planned to kill himself in the bloody rampage but ultimately lost his nerve and surrendered, Texas Gov. Greg Abbott said.

U.S. Senator John Cornyn said the shotgun was of the ultra-deadly sawed-off variety and that investigators were trying to determine whether the shortened barrel was legal.

The suspect also had a cache of improvised explosive devices placed in the school and surrounding areas, including pipe bombs and a "pressure-cooker" device, Santa Fe Police Chief Jeff Powell said, warning members of the community to call 911 should they come across anything suspicious looking.

A law enforcement official told CNN that an 18-year-old student was also detained for questioning in the aftermath of the deadly shooting.

Dimitrios Pagourtzis (or Dimitri Pagourtzis), 17, was identified as the shooter at Santa Fe High School in Santa Fe, Texas on Fri., May 18, 2018. (Galveston County Jail)

Among the ten people injured in the barrage was a school resource officer, who was in critical condition.

Student Rome Shubert, 16, was grazed in the back of the head by a bullet.

"I'm so greatful (sic) and blessed that god spared me life today. Today I was shot in the back of the head but i am completely okay and stable," he wrote on Twitter.

Dustin Severin, a 17-year-old student, told KPRC he saw Pagourtzis in a hallway before the gunfire erupted, sporting his usual attire.

"He wears a trench coat every day, and it's like 90 degrees out here," the teen said, adding the suspected gunman was a loner who kept to himself.

Here, photos from Pagourtzis Facebook page show a t-shirt that reads "Born To Kill" and a military uniform with Nazi-related insignia. (Facebook)

Two weeks before the shooting, Pagourtzis allegedly posted photos on Facebook showing a custom-made black t-shirt emblazoned with the phrase, "Born to Kill," and a trench coat decorated with Nazi, communist, fascist and religious symbols.

Abbott said authorities uncovered entries from the shooter's journal that appeared to indicate he was suicidal.

Pagourtzis appeared in court late Friday and bowed his head with his wrists shackled.

"Yes sir," he said when asked by the court if he was a citizen of the United States.

"No sir," he said when asked if he was out on bond for any other charge.

Santa Fe is located outside of Houston, Texas. (New York Daily News)

Pagourtzis did not enter a plea. He was denied bail and asked to be represented by a court-appointed attorney.

Student Angelica Martinez said it was a "normal-like class day" until the fire alarm started to blare.

"So we followed the fire drill procedures. And then we went outside. Like we were all standing there, but not even five minutes later, we all start hearing gunshots," the 14-year-old told CNN.

That's when everyone started to run, despite teachers urging them to remain calm, she said.

Three patients were admitted to the University of Texas Medical Branch, among them a police officer undergoing surgery for a gunshot wound to his arm, according to KHOU.